Bottom Line:
The global herbal products market has grown in recent years, making regulation of these products paramount for public healthcare.As morphology-based identification is often difficult or impossible, the identification of processed material can be aided by molecular techniques.The TLC-test is more cost- and time-efficient, but DNA barcoding is more powerful in determining the identity of adulterant species.

ABSTRACTThe global herbal products market has grown in recent years, making regulation of these products paramount for public healthcare. For instance, the common horsetail (Equisetum arvense L.) is used in numerous herbal products, but it can be adulterated with closely related species, especially E. palustre L. that can produce toxic alkaloids. As morphology-based identification is often difficult or impossible, the identification of processed material can be aided by molecular techniques. In this study, we explore two molecular identification techniques as methods of testing the purity of these products: a Thin Layer Chromatography approach (TLC-test) included in the European Pharmacopoeia and a DNA barcoding approach, used in recent years to identify material in herbal products. We test the potential of these methods for distinguishing and identifying these species using material from herbarium collections and commercial herbal products. We find that both methods can discriminate between the two species and positively identify E. arvense. The TLC-test is more cost- and time-efficient, but DNA barcoding is more powerful in determining the identity of adulterant species. Our study shows that, although DNA barcoding presents certain advantages, other established laboratory methods can perform as well or even better in confirming species' identity in herbal products.

f5: DNA barcoding of Equisetum arvense and E. palustre based on two markers (matK & trnH-psbA).The phylogenetic tree was reconstructed with a Maximum Likelihood analysis based, using E. variegatum as an outgroup. Bootstrap support values are given above respective branches.

Mentions:
The two plastid markers we used for the DNA barcoding of E. arvense and E. palustre resolve the samples into two well supported, monophyletic clades, shown in Fig. 5. We were able to amplify DNA from two of the herbal products, only; one was resolved within the E. arvense clade (BP 100). The other, which was shown to be a mixture from the TLC-test (B – Bulgaria), is recovered with the E. palustre (BP 77) clade (Fig. 5). For both barcoding regions, we found 36 substitutions (25 for matK and 11 for trnH-psbA) that can distinguish E. arvense and E. palustre. Some of them are unique to each species and others are shared with other species, but not between E. arvense and E. palustre (Table 1).

f5: DNA barcoding of Equisetum arvense and E. palustre based on two markers (matK & trnH-psbA).The phylogenetic tree was reconstructed with a Maximum Likelihood analysis based, using E. variegatum as an outgroup. Bootstrap support values are given above respective branches.

Mentions:
The two plastid markers we used for the DNA barcoding of E. arvense and E. palustre resolve the samples into two well supported, monophyletic clades, shown in Fig. 5. We were able to amplify DNA from two of the herbal products, only; one was resolved within the E. arvense clade (BP 100). The other, which was shown to be a mixture from the TLC-test (B – Bulgaria), is recovered with the E. palustre (BP 77) clade (Fig. 5). For both barcoding regions, we found 36 substitutions (25 for matK and 11 for trnH-psbA) that can distinguish E. arvense and E. palustre. Some of them are unique to each species and others are shared with other species, but not between E. arvense and E. palustre (Table 1).

Bottom Line:
The global herbal products market has grown in recent years, making regulation of these products paramount for public healthcare.As morphology-based identification is often difficult or impossible, the identification of processed material can be aided by molecular techniques.The TLC-test is more cost- and time-efficient, but DNA barcoding is more powerful in determining the identity of adulterant species.

ABSTRACTThe global herbal products market has grown in recent years, making regulation of these products paramount for public healthcare. For instance, the common horsetail (Equisetum arvense L.) is used in numerous herbal products, but it can be adulterated with closely related species, especially E. palustre L. that can produce toxic alkaloids. As morphology-based identification is often difficult or impossible, the identification of processed material can be aided by molecular techniques. In this study, we explore two molecular identification techniques as methods of testing the purity of these products: a Thin Layer Chromatography approach (TLC-test) included in the European Pharmacopoeia and a DNA barcoding approach, used in recent years to identify material in herbal products. We test the potential of these methods for distinguishing and identifying these species using material from herbarium collections and commercial herbal products. We find that both methods can discriminate between the two species and positively identify E. arvense. The TLC-test is more cost- and time-efficient, but DNA barcoding is more powerful in determining the identity of adulterant species. Our study shows that, although DNA barcoding presents certain advantages, other established laboratory methods can perform as well or even better in confirming species' identity in herbal products.